J. Phys. I France
Volume 3, Numéro 8, August 1993
Page(s) 1873 - 1888
DOI: 10.1051/jp1:1993218
J. Phys. I France 3 (1993) 1873-1888

Bond-orientational order in liquid aluminium $_{\rm {80}}$-transition metal $_{\rm {20}}$ alloys

M. Maret1, F. Lançon2 and L. Billard2

1  Laboratoire de Thermodynamique et Physico-Chimie Métallurgiques (CNRS URA 29), ENSEEG, BP75, 38402 St-Martin d'Hères Cedex, France
2  Département de Recherche Fondamentale sur la Matière Condensée, SP2M/MP, CENG, BP 85X, 38041 Grenoble Cedex, France

(Received 23 December 1991, revised 18 February 1993, accepted 8 April 1993)

The structures of liquid Al $_{\rm {80}}$Mn $_{\rm {20}}$ and Al $_{\rm {80}}$Ni $_{\rm {20}}$ are simulated by molecular dynamics using interatomic potentials derived from neutron diffraction data. For these two alloys, the generated three dimensional particle configurations are consistent with the experimental partial pair correlation functions. The characterization of the local symmetries by both the construction of the Voronoï polyhedra and the calculation of the second-order invariants of spherical harmonics allows us to confirm the existence of a local icosahedral order in the quasicry stal -form i ng liquid Al $_{\rm {80}}$Mn $_{\rm {20}}$ and its absence in liquid Al $_{\rm {80}}$Ni $_{\rm {20}}$ about 70 K above the liquidus line. Molecular dynamics simulations of the corresponding supercooled liquids show that this order increases strongly for Al $_{\rm {80}}$Mn $_{\rm {20}}$ and starts to develop for Al $_{\rm {80}}$Ni $_{\rm {20}}$. An improvement of the agreement between the experimental and calculated pair correlation functions by the reverse Monte Carlo method yields liquid configurations characterized by the same most frequently observed Voronoï polyhedra as those obtained in the molecular dynamics configurations, but with lower percentages.

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